<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Loading Animation</title>
    <style>
        * {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

section {
    height: 100vh;
    width: 100%;
    background: #000;
    display: flex;
    align-items: center;
    justify-content: center;
}

section .loader {
    height: 25px;
    width: 25px;
    position: relative;
}

.loader .ball {
    position: absolute;
    height: 25px;
    width: 25px;
    border-radius: 50%;
}

.loader .upper {
    left: 0;
    top: -25px;
    background: #2da2ff;
    animation: upper 1s infinite;
}

@keyframes upper {

    50%,
    100% {
        top: 25px;
    }
}

.loader .right {
    bottom: 0;
    right: -25px;
    background: #ff337a;
    animation: right 1s infinite;
}

@keyframes right {

    50%,
    100% {
        right: 25px;
    }
}

.loader .lower {
    bottom: -25px;
    right: 0;
    background: #ffff00;
    animation: lower 1s infinite;
}

@keyframes lower {

    50%,
    100% {
        bottom: 25px;
    }
}

.loader .left {
    left: -25px;
    bottom: 0;
    background: #00ff00;
    animation: left 1s infinite;
}

@keyframes left {

    50%,
    100% {
        left: 25px;
    }
}
    </style>
</head>

<body>

    <section>

        <div class="loader">
            <div class="upper ball"></div>
            <div class="right ball"></div>
            <div class="lower ball"></div>
            <div class="left ball"></div>
        </div>

    </section>

</body>

</html>